Such a mass balancing mechanism follows from EP 1 304 450 A2, which is considered a class-forming patent. The mass balancing mechanism proposed in that publication is used for balancing the free second-order mass forces of a four-cylinder in-line engine and comprises two unbalanced shafts rotating in the opposite direction at twice the crankshaft rotational speed. These are supported in four places and each of these has two successive shaft sections with eccentric centers of mass for generating the imbalance. The diameter of the inner bearing journal connecting the shaft sections is significantly smaller than the surrounding diameter of the shaft sections, so that the substitution of the radial plain bearing provided at this bearing point by a radial roller bearing that is more favorable with respect to friction losses is not possible with a non-divided bearing ring for reasons of assembly—however, a roller bearing with a divided outer ring could be used here, in which, however, due to the then unavoidable step formation on the outer raceway, functional and service life limitations are to be expected. Also, the other three bearing journals of each unbalanced shaft have a plain radial support at the associated bearing points.
From EP 0 243 683 A1, a mass balancing mechanism follows with unbalanced shafts supported in three places and, in this case, completely by rollers. Their geometry with only one shaft section generating the imbalance, however, allows the assembly of non-divided roller bearings without a problem. This applies in the same way for the unbalanced shaft that is disclosed in FR 2 619 881 A1 and is supported, in contrast, by plain bearings instead of roller bearings on the drive-side end section.